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By JAMES A. VEASEY

SINCE the World War, excepting for a few brief periods of relief, the American petroleum industry has been obliged to meet its important economic responsibility to this nation hampered by the maladjustment that inevitably follows a marked and unwholesome over-production of its raw material, crude oil. Despite the warnings of the Federal Oil Conservation Board and the endeavors of many of the leaders in the business to stem the flow of oil from the wells of the country, the evil ,not only persists but, at the moment, seems more malignant than ever before. Unless the local and temporary restraints on drilling and production now in effect in California, Wyoming, Texas, and Oklahoma are continued, and, indeed, unless stricter and more comprehensive measures of the same sort are imposed and adhered to by the industry in those States, over-production in the enterprise during the current year will be more pronounced than in any other period in history.

Jan 1, 1929

By H. S. Bostock

"The study of the geology of Mayo district began in 1900 with R. G. McConnell's exploration of Stewart river; and has been carried on intermittently for the Geological Survey of Canada by J. Keele; D. D. Cairnes; W. E. Cockfield; C. H. Stockwell; and the writer. It has revealed a thick group of schists; quartzites; and crystalline limestones; almost certainly Precambrian in age; placed in the Yukon group; and a group of younger intrusive igneous rocks varying in composition from granite to gabbro. These include bodies of many sizes and forms; from stocks 8 miles across to small dykes and sills.Prospecting in the district began about 1897 and has disclosed the presence of gold, silver, lead, tungsten, tin, zinc, antimony, copper, arsenic, manganese, and mercury, both in placer and lode deposits . Of these metals gold, silver, and tungsten have been produced from placer deposits, and silver, lead, and gold from lodes. This paper deals only with some structural relationships of the lode deposits, generally referred to as the silver-lead veins, which have yielded the greater part of the mineral production of the area. From 1938 to 1941 the geological mapping of the district for publication on a scale of 4 miles to 1 inch was carried out by the writer, and the ideas expressed here are based on this work. No comprehensive detailed study of the silver-lead veins has been made, but the mapping has brought to light several important facts. The rocks of the Yukon group, although of a striking sameness throughout their section, can be divided into a number of distinguishable members by means of which the main structures can be traced . The most important and readily distinguishable rock in the group is referred to here as the quartzite member. This is composed of quartzite and schist in about equal proportions. The quartzite is resistant to erosion and forms most of the outcrops of the'member and the peaks of the Gustavus mountains and mount Haldane (Lookout)."

Jan 1, 1954

By Keith P. Bingham

A total transportation system providing for delivery of finished products to customers and raw materials to the plant is one of the key elements contributing to Dravo Lime Co.'s success. Dravo Lime operates one of the largest noncaptive lime and limestone plants in the US at Maysville, KY, where products produced can cost as much to deliver as they do to manufacture, depending on the product itself, its destination, and mode of transportation. With delivery costs comprising a significant portion of total costs for its products, Dravo Lime has made total transportation services an integral part of its business strategy. Prices for most products produced at Maysville are quoted f.o.b. destination. In short, Dravo Lime's Distribution Department relies on the approach that says to customers: "Leave the delivery to us." The 0.9-Mt/a (1-million stpy) Maysville facility, located about 121 km (75 miles) east of Cincinnati, OH, on the Ohio River, primarily produces sulfur-absorbing Thiosorbic lime used by coal-fired electric utilities as a scrubber reagent to remove SO2 from stack gases. The product is currently supplied to eight power plants in the Ohio River valley region which extends through portions of Kentucky, Indiana, Ohio, West Virginia, and Pennsylvania. The plant ships approximately 907 kt (1 million st) of lime and a comparable amount of limestone fines each year. In addition, it arranges for delivery of about 181 kt (200,000 st) of coal to the plant. Lime is transported by covered hopper barges, covered rail cars, covered dump trucks, and pneumatic trucks. It is transferred from barges to storage silos and trucks at a terminal on the Ohio River near Marietta, OH. At another terminal near Aliquippa, PA, lime is transferred from barges to silos, trucks, and rail cars. Future plans call for rail-truck transfer terminals. To produce lime from limestone at the Maysville plant, about 181 kt (200,000 st) of coal is burned annually in three coal-fired kilns. In transporting this coal from the mine to Maysville, Dravo takes maximum advantage of opportunities for reloading carriers with limestone for outbound backhaul movement. Coal, shipped from southeastern Kentucky mines in rail cars, is transferred to barges at a river terminal in West Virginia. After it is unloaded at Maysville, the barges are cleaned with a front-end loader and then reloaded with limestone. Limestone also is backhauled in connection with truck deliveries of coal. The economics of using backhaul shipments has permitted Dravo to enter into markets in which Maysville limestone otherwise would not be competitive. The company plans to backhaul limestone in empty open hopper cars in the future. As part of its ongoing assessment of the distribution system that supports the Maysville operation, Dravo Lime recognizes that a new environment has developed between shippers and carriers because of regulatory changes in the railroad and trucking industries. Although dry bulk shipments by barge to and from Maysville have always been unregulated, other forms of transportation have not. With railroads and motor carriers now approaching varying degrees of deregulation, contracts and agreements are replacing tariffs, and rate negotiations are becoming a daily activity. Dravo Lime plans to take advantage of these transportation changes, all of which may be beneficial to both its plant and its customers.

Jan 10, 1982

By Jorge Olivari Ortega

"Los incas desarrollaron un censo que les permitía planificar el desarrollo socio-económico de la región, como la actividad minera aurífera. En ese sentido, el gobierno del inca Mayta Cápac elaboró un sistema estadístico, a partir de los quipus para registrar toda la información y obtener el máximo provecho de los recursos existentes. Por ello, el presente texto describe el proceso del método estadítico que permitió a los incas adquiirir el tributo que habían programado. Para ello, se utilizaron los cordones de variados colores (quipus) para diferenciarlos en cada actividad como el amarillo que significaba la actividad minera aurífera. En estos cordones, los quipucamayoc registraban la cantidad de oro producido durante la mita minera o con los mitimaes en los yacimientos auríferos el número de personas que participó, la cantidad de días, las herramientas, los viveres, los vestidos, etc. Las herramientas utilizadas en la explotación de los yacimientos auríferos tipo lavadero, son las mismas que en la actividad agrícola, ya que en ambas se requieren remover la tierra: en la agricultura para sembrar las semillas, y en la minería aurífera, para lavarla y obtener las partículas de oro."

May 1, 2016

By Harry Sutcliffe, Francis M. Keville

The paper describes the, impact of the geotechnical exploration program on the line and grade of the tunnels and the shaft configuration on the Red Line Extension N.W. in Cambridge and Somerville, Massachusetts, and comments on several aspects of the implementation of the project.

Jan 1, 1983

By Gregory Yates

INTRODUCTION Project Description The Silver Line is a Bus Rapid Transit (BRT) Line and is Boston?s newest transit service. Silver Line Phase I extends along Washington Street entirely on the surface in priority bus lanes from Dudley Station in Roxbury through the South End and Chinatown neighborhoods to downtown Boston. The Phase I opened in July 2002. Silver Line Phase II consists of an underground transit tunnel from South Station to the South Boston Waterfront with underground stations at Courthouse and World Trade Center to Silver Line Way east of D Street. Phase II continues through the Ted Williams Tunnel to all the terminals at Logan Airport, and on the surface to the Boston Marine Industrial Park and City Point. Phase II opened in December 2004. Silver Line Phase III is a one mile tunnel connection to the existing Phase II tunnel in the vicinity of South Station and will eventually portal on Tremont Street just north of Marginal Road. After leaving the portal, the buses will use dedicated bus only lanes on the surface roadway network to connect to the Phase I service. Figure 1 shows the alignment of the Silver Line upon completion of the Phase III project.

By Kevin Beirne

Most people involved in the mining industry are familiar with student-industry co-op work-study programs. Many colleges and universities have used them for years. Northern College’s Haileybury School of Mines student co-op program adds a new dimension of productivity to the college and the mining industry. The college is located in Hailey-bury, Ontario, Canada. An example of the program’s success is the school’s relationship with Sabin Metal’s SMC (Canada) Ltd.’s McAlpine Mill in Cobalt, Ontario. Students gain practical knowledge and experience while industry gains an eager-to-learn worker. And many of the college’s advanced research services are made available to industry to supplement their own capabilities. The McAlpine Mill was established to provide custom milling of slags and ores. It also recovers metal values from other products of the primary and secondary precious metal industries.

Jan 1, 1999

By K Cameron, S Strohmayr, J Wallace

In 2012, a single module heavy medium cyclone plant (HMP) was installed at the Glencore Zinc’s (then Xstrata Zinc) McArthur River lead zinc mine. The HMP formed the first part of the MRM Phase 3 Project to increase run of mine (ROM) capacity from 2.4 to 5.5 Mt/a.The purpose of the HMP is to remove liberated gangue from the crusher product at minimal loss of valuable mineral. The McArthur ores are very finely disseminated requiring a fine primary grind size prior to rougher flotation. Rejecting waste prior to grinding therefore offers significant power and grinding media savings. The plant was designed to treat only those ores with a reasonable upgrade ratio at the target zinc recovery across the HMP of 95%.On this basis, a 1.8 Mt/a single module plant was built based on 250 t/h feed rate and 82% availability. In contrast to existing base metal heavy medium plants in Australia, the MRM Flow sheet utilised the principles in modern coal heavy medium cyclone plant design. Since commissioning, the plant feed rate has been significantly increased and is now normally operated up to 540 t/h (dry basis).Although this throughput increase is partially due to debottlenecking work, it is also attributable to the conservative design parameters for base metal heavy medium cyclone circuits in comparison to those used in equivalent coal circuits.This paper discusses Flow sheet design and compares traditional base metal design parameters with those achieved at MRM and those of modern coal plants. It provides information on plant capital and operating costs and the net savings realised by its installation. In addition to power and grinding cost savings, the paper also highlights the savings in water through rejection of near dry waste and reduction of tailings pumped to the storage dam.CITATION:Wallace, J, Strohmayr, S and Cameron, K, 2015. McArthur River Mine heavy medium plant – the benefits of applying modern coal plant design principles to base metal heavy medium separation, in Proceedings MetPlant 2015, pp 311–323 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

Thank you chairman, good afternoon ladies and gentlemen. In my talk this afternoon I intend to cover a brief history, some of the recent experiences and an overview of the McArthur River project.If we consider the themes of this forum, Obstacles and Opportunities, I can confidently say that in attempting to develop the McArthur River deposit Mount Isa Mines Limited (MIM) must have encountered almost every obstacle that can be imagined. However the large size and the high grade of the deposit has ensured an opportunity, from which it is very difficult to walk away from.The McArthur River Here's Your Chance (HYC) Deposit is located in the Northern Territory of Australia. It was discovered by Mount Isa Mines Limited geologists in 1955 and is one of the largest known sedimentary stratiform zinc-lead-silver deposits. The deposit has been the subject of numerous investigations and considerable expenditure culminating in a major feasibility study in 1979. There were a number of factors which prevented development, these being the size of the project, the fine grained mineralization, geographical location, market, social and capital cost. The latter had been estimated in the 1979 study to be $800 million at that time.

Jan 1, 1993

By T. S. Grewal, S. C. Gupta, H. Natarajan, T. W. McQuade, N. Nejibulloev-Mamedov

Cigar Lake is one of the world’s largest high-grade uranium mines. The ore mined at Cigar Lake is milled at Orano Canada Inc’s (Orano) McClean Lake mill. The average Cigar Lake ore uranium grade since the start of mining activities in 2014 is 17.8% U (range 8– 28%). To achieve budgeted production of 18 M lbs U3O8/yr the required average feed tonnage to the mill is about 45 kt/yr. Arsenic, occurring as arsenides and sulpharsenides, is one of the major elements of concern associated with Cigar Lake ore. The leaching process is a sulphuric acid leach under oxidizing conditions at near atmospheric pressure. The presence of arsenic in the ore consumes oxidant in leaching as well as ferric sulphate in tailings preparation for arsenic sequestration. The average arsenic grade since the start of mining at Cigar Lake is 0.57% As. Further, the ore is hosted in a matrix of sandstone and clay, which results in poor settling in CCD. The average uranium grade for the balance of Cigar Lake Phase 1 ore is expected to drop to 12.5% U and the average arsenic grade is expected to increase to 1.6 % As, with an annual average peak of 2.5%. Therefore the tonnage throughput required to sustainably meet the production target will increase to 55 kt per year. Orano partnered with Hatch Ltd. (Hatch) to perform a gap analysis study to identify key circuits and equipment in the mill that would require debottlenecking. A METSIM mass balance model of the McClean Lake mill was generated and validated with actual mill operating data. Various feed scenarios were then studied, and the outcome was a traffic light table, which highlighted feed scenarios that exceeded installed capacity of major equipment and circuits. The results provided the basis for the PDC for the pre-feasibility study. This paper will outline the results of the gap analysis, the mass balance model, the feed scenarios and the study undertaken to prepare the McClean Lake mill for the change in ore quality from Cigar Lake.

Jan 1, 2020

By L. O. Storey

The McDermitt mine was found as a separate mercury ore-bearing occurrence approximately 305 m (1000 ft) northeasterly and in a different geologic setting from the old Cordero mine, which had been the district's major producer. The following briefly describes the discovery of the new deposit and the Placer Amex lnc. involvement. The Cordero mining property was under lease by Sierra Mineral Management from the owner Fred H. Lenway in February 1971, when the property was brought to the attention of Placer Amex Inc. (known at that time as American Exploration and Mining Co.) by Richard F. Hewlett of Sierra Mineral Management. The property was first examined by Amex geologists in the spring of 1971, who reported favorably on the project. During that year, Sierra Minerals Management had retained Dr. Larry Walters as a consultant. He proceeded to drill test mercury soils anomalies which he had found northeast of the old Cordero mine in an area overlain by recent alluvium and gravel. An area known as the D area was subsequently blocked out and ascribed a tonnage of about 18 1 kt (200,000 st) which occurs in the vicinity of the eastern edge of the currently defined McDermitt ore body. This mineralization was found in flat lying mercury-bearing lakebeds, unlike the steep structurally controlled ore which was mined in the old Cordero mine. It became apparent to Placer Amex that since the chances of much more extensive ore were good in such a geologic environment, additional exploration was warranted. A joint venture was formed in October 1972 by American Exploration and Mining Co. and Sierra Mineral Management to further explore the Cordero property. The project exploration was fully funded and managed by Amex. Sampling began by Placer Amex in the D area where an open trench had exposed the lakebed ore. Visible cinnabar could not account for the high-grade mercury assays taken from the trench, and an unknown mercury mineral was suspected. Subsequent work established the presence of a chlorine-bearing mercury sulfide which may have enriched the lakebeds as a secondary supergene mineral. Early identification of the mercury-bearing mineral corderoite (Hg3Cl2S,) aided in the geologic concepts for the ore occurrence and was helpful in exploring for the expansion of the D area. Corderoite was found occurring with cinnabar in the lakebeds, and in places it is a major contributor. Specimens of the unique ore were given to Dr. Eugene E. Foord and Dr. Pieter Berendsen at Stanford University, who subsequently identified the chemical and crystallographic makeup of the new mineral and described it for the first time as a naturally occurring substance. Metallurgical work on mercury recovery from the newly described mineral was carried out by the Placer Development Ltd. laboratories in Vancouver, and an acceptable recovery system was worked out together with a planned mill design. Step out drilling from the D area by Placer Amex Inc. encountered extensive flat lying lakebed ore. The McDermitt ore body, as subsequently defined by drilling, was found to contain 2.7 Mt (3 million st) of open pittable ore, containing approximately 5 kg/t (10 lb per st) Hg. The ore body gently dips to the north and is found lying mainly in claybeds just above an opalite breccia blanket which overlies the earlier volcanics. Some ore is also found in the opalite breccia. The mine and mill were constructed under an operating joint venture with Placer Amex Inc. and Sterling Mineral Ventures, and production began in June 1975 at the rate of 20,000 flasks per year. The mine is currently in progress.

Jan 1, 1985

By D. S. Harries, R. I. L. Guthrie

"The use and development of scientific disciplines involved in heat transfer technology, related in general to steel masses and in particular to batch annealing, is demonstrated.The measurable benefits of cooperation are tabled; on industry's side, this includes a 10 to 20 per cent decrease in annealing time, and a corresponding higher productivity potential. The returned benefits to the academic engineer include the development and refinement of new computer algorithms related to heat transfer mechanisms.IntroductionThe object of this discussion is not really to describe an improvement in the batch annealing operation, but to use the project as an example of joint work between industry and the academic field. Both parties have derived a number of substantial benefits. These benefits will be listed, of course, but the batch anneal project will be used just as a typical example of cooperation. Why it happened will be explained, what actually happened will be described and finally some thoughts about areas in the field of heat transfer, where cooperation will continue in the future, will be highlighted. The paper will close with a message.Industry OverviewAt the outset, perhaps it should be understood that, in general, the Research Department at Dofasco believes that the universities and their staff are not destined for the problem-solving role in industry. Its opinion is that the university staff is best suited to the gathering and dissemination of knowledge. There are other more professional problem solvers for industry, including the steel industries' own individual investigation groups. Dofasco, therefore, looks to its academics for consultation. It benefits by bouncing ideas off them, and through rubbing shoulders with them in such a way that their knowledge can be tapped, and thus establish more effective scientific routes. In addition, the younger and brighter engineer s can broaden their scope through the intellectual contact with experts. The university professors can, it is believed, benefit through closer contacts with result-orientated research. They can also develop an appreciation of the fiscal control necessary for industrial investigations, without government subsidies, grants, etc., and with massive overheads."

Jan 1, 1982

By M. Mirnezami, J. A. Finch

The McGill component of the consortium contributed detailed examination of the electrokinetic properties of the constituent minerals, primarily pentlandite and serpentine. Mineral specimens were derived from an ore sample; mineralogical examination showed the serpentine was predominantly clinochrysotile, a fibrous mineral responsible for much of the flotation separation problem. The study included design of a novel sedimentation potential measuring device to classify the surface charge of the ore and electrophoresis measurements on single and mixed minerals which progressively approached flotation conditions. The sedimentation potential measurements provided a general association between surface charge and the visual state of aggregation as a function of pH. The electrophoresis experiments started with single minerals in a background of indifferent electrolyte and progressed to mixed minerals in a background of supernatant derived from an ore sample. The single mineral tests supported the suspected electrostatic interaction, i.e., hetero-coagulation, at flotation pH 9-10. The mixed mineral tests demonstrated this interaction and also revealed hetero-coagulation with Mg(OH)2 precipitates, derived from the supernatant. This interpretation was confirmed by optical and electron beam imaging. A series of agents, CMC, polyphosphate, soda ash, EDTA, were examined to disperse the system. To accommodate the small mass of single mineral available a novel turbidity measurement using a UV/Vis spectrophotometer was introduced. Selected conditions were used in contact angle and small-scale flotation tests.

Jan 1, 2011

By Geo. D. Furse

"The information that has accumulated regarding the geology of the McIntyre mine is the result of work by several geologists and, as might be anticipated, their conclusions have varied. The writer has been at the mine only a few years and due to wartime conditions has not been able to study and review the mine's geology as thoroughly as his predecessors. Where the writer's conclusions differ from those of previous authors, it should be noted that he has been unable to re-map all the workings in which flow contacts are exposed, but has endeavoured to describe the structure as indicated by the evidence he has been able to observe. He wishes to thank H. G. Skavlem and H. S. Robinson for their constructive criticism of this paper, and McIntyre Porcupine Mines, Limited, for permission to present it. A list of references is appended.The McIntyre mine is in the central part of the Pearl Lake section of the Porcupine gold area. It includes the ""bed of Pearl lake, twenty-two claims to the north of the lake, and the Platt Vet lot to the southeast. It is bordered on the west by the Hollinger and on the east by the Coniaurum property. The chief ore-bearing veins on the upper levels lie very close to the north shore of the lake, but some occur under the lake, and others of lesser importance are found to the southeast. The most important veins are Nos. 3, 5, 7, 10, and 25. Some of the veins extend into the Hollinger. on the west and others cross the east boundary into the Coniaurum. The total production since the commencement of milling in 1912 to the end of March 1947 has been $168,448,218 in gold and silver from the milling of 17,690,963 tons of ore."

Jan 1, 1954

Mr. Chairman, distinguished guests, ladies and gentlemen. Thank you for asking me to your conference, with its most fundamental and appropriate topic of 'Investment in Mining'. I must confess at the outset that I am one of those Australians who has rarely visited your fair land of New Zealand. This is in fact only my third visit, with all three related to Institute Conferences, and all much too brief. In so many ways your country provides a counterpoise to ours, despite the obvious disparities in size and population. And I am not only referring to the Bledisloe Cup! We would certainly each be much more lonely without the other, in this strange long-lost corner of the globe û if globes can have corners. Such an important factor in common in our shared heritages has been the mineral industry we have won from our alluvials and our rocks û especially for gold. So much of the major mineral developments which have supplied the world's appetite for metals and fuels in the past two hundred years has come from the countries settled in that period by people from Europe, especially those from the British Isles. So much of the technology for mineral and metal extraction has come from the skills of those people in New Zealand and Australia. And so much of the further development of metal processing and manufacturing of productive equipment has come from those people and from their cousins throughout the world. It is, I believe, a fair question to ask why we have failed to build on those early and considerable successes, and why we have in so many ways apparently been so content to allow others to add value to our raw materials, and to take our technological developments on to levels far beyond those that our domestic markets could sustain.

Jan 1, 1988

By The Staff

THE property of McKenzie Red Lake Gold Mines, Limited, consists of eleven claims located on McKenzie island in Red lake. The mine is about 4,Y:l miles by water from the Howey townsite on the same lake, and about 95 miles north of Kenora, Ont. (see Figure 4). Mail and express are flown-in daily, winter and summer, from Sioux Lookout, Hudson, Kenora, and Winnipeg. All heavy supplies are freighted-in during the summer over a water route, using four marine railway portages, from Hudson, Ont., a distance of about 180 miles. During the winter, freighting over the same route is clone by tractor if necessary, but costs are three to four rimes the summer rate. Due to these conditions, large inventories of supplies must be kept on hand, varying from a spring minimum of $45,000 to a peak of $110,000 early in November. The average cost of all freight brought in from steel during 1937 was $0.01 per pound.

Jan 1, 1938

By H. Clare Horwood

"Three types of structures, the main shear zone, the north shear zone, and a series of hanging-wall fractures, contain all the orebodies so far discovered at the McKenzie Red Lake mine. Lenses and veins of quartz in these zones and fractures are the sources of the ore. The ore-bearing structures are unusual in that they are in a complex intrusive mass known as the McKenzie-Gold Eagle stock. They are believed to have been produced by compressive stresses from the south andsouthwest.The mine is on the northeast side of McKenzie island, in Dome township in the central part of the Red Lake area. The original discovery, the main shear zone, was made in 1928, about 3 years after the property was staked, by M. L. Bouzan who was in charge of prospecting and development work on the property. Subsequent diamond drilling and underground exploration led to the installation of a mill, which came into production early in 1935. The hanging-wall fractures were found branching out from the main shear zone during development work on the 350-foot level. The north shear zone was discovered in 1940.From 1935 when the mill began operation until the end of 1946 total production from the mine was approximately 269,349 oz. gold and 69,317 oz. silver, having a value of $9,679,739, recovered from 823,527 tons of ore.GENERAL GEOLOGYThe McKenzie-Gold Eagle stock has a total length of approximately 1 ½ miles and a width of about ½ mile. It was intruded into a complex synclinal fold in Timiskaming sediments. The sediments, which have been cut in only one place in the underground workings, are principally wellbedded greywackes. The stock is composed of large masses of diorite and granodiorite, a small mass of hornblende pyroxenite, and basic dykes of two ages. The diorite occurs as irregular masses in large measure surrounded by the granodiorite that it intrudes. It contains tabular crystals of andesine, having a maximum length of3/4 inch. The hornblende pyroxenite is an elongated lens or dyke in the diorite. The granodiorite masses occupy about two-thirds of the stock. Along its eastern side the main mass tends to become darker and more dioritic toward the diorite contact.Basic dykes of pre-vein and post-vein age are the youngest intrusive rocks at the mine."

Jan 1, 1954

By M. Jorgensen, I. Markland, D. Shuck

"The McLaughlin Mine owned by Homestake Mining Company is located 70 miles northeast of San Francisco in California's coastal range. The mine began operations in February of 1985. The mill currently processes 3,000 short-ton per day of sulfide ore that has an average grade of 0.15 ounces of gold per ton, plus another 3,000 tons per day in a newly completed oxide circuit. Annual production from the mine totals over 200,000 ounces.The sulfide ore extraction process involves three basic steps, grinding, oxidation of sulfide minerals in an autoclave, and cyanide leaching for recovery of gold in a carbon-in-pulp circuit. This process, which incorporates a new technology where oxidation of sulfide minerals is conducted prior to cyanide leaching to facilitate gold recovery, was successful from start-up. However, limitation in the grinding mills initially limited sulfide tonnage throughput.This paper discusses modifications made in the grinding circuit, both mechanical and operational, to resolve it deficiency. The SAG mill, in particular, was unable to achieve design tonnage initially and proved to be most troublesome. Complications occurred due to the hardness and variability of ore being processed, short component life, and a lifter /liner arrangement that had to be tailored to the particular circumstances at McLaughlin. IntroductionHomestake Mining Company's McLaughlin Mill, located in northern California, was designed to process a refractory gold ore at a rate of 3,000 tpd to render the ore amenable to cyanidation. Seven years transpired between discovery of the near-surface ore body in 1978 and the February, 1985 plant start-up. Development of the McLaughlin mill and open pit gold mine hinged on the use of autoclave technology to achieve design recoveries."

Jan 1, 1991

By Myron W. Mellor

Our efforts at McNally, to find a better way to mechanically separate particles from liquid in a slurry have led to the development of two new centrifuges. The first unit utilizes a slotted opening screen as the filter media and retains all plus 200 Mesh and most of the 200 by 300 Mesh particles. The second unit is a solid bowl centrifuge with a novel method of removing the solids and delivers an effluent containing as little as 300 PPM solids in suspension. The first unit was designed to separate particles in the range of about 1 MM x 0 or smaller top size from the liquid slurry and produce solids having low surface moisture content, and a liquid concentrate containing a low percentage of solids. A prototype of this unit has been in the field undergoing tests for over two years. A few of these test results are shown in Tables I & 11. Testing has been mostly limited to the field of coal, how- ever this does not mean that the machine would accept only coal slurries. The machine has produced a dewatered product having as low as 5.5% surface moisture, and an effluent containing as low as 1.4% solids and handled slurries containing from 15 to 50% solids by weight.

Jan 1, 1975

By M. E. Wilson

"The property of McWatters Gold Mines, Limited, is in the east-central part of Rouyn township and about 6 miles east-southeast of the town of Rouyn. It includes 35 claims, the group of 5, staked originally, and 30 claims acquired in later years. The Rouyn-Val d'Or road and the Noranda Senneterre branch of the Canadian National railway both pass within a few hundred feet of the mine.The group of claims in which the mine occurs was first staked in 1922, but gold was not discovered until August 1932 when a schistose zone including veins of quartz carrying considerable free gold was laid bare in a stripped area in the northeastern part of claim R.11604. Diamond drilling undertaken in 1932, and continued into 1933, shouwd that the gold extended for at least 1,000 feet along the strike. A 3-compartment shaft was sunk to 418 feet in 1933. A mill having a capacity of 50 tons a day was constructed in 1934, and enlarged to 150 tons in 1935. Production began in 1934 and continued without interruption to June 1944. Except for a few diamond drill holes, there have been no operations on the property since that time. The maximum depth of the mine workings is 1,50) feet. A total of 368,013 tons of ore having a value of $3,946,752 and an average grade of $11.04 was mined during the years of operation.GEOLOGYThe ore mined from the property occurred within the south limb of an eastward plunging syncline of volcanics and sediments cut off on the north by the Cadillac-Bouzan Lake fault. Because the rock formations within the syncline have been severed from those outside with which they were originally continuous, their correlation is based almost wholly on lithological similarity. They include an irregular middle zone of conglomerate and greywacke underlain by north and south bands of andesite agglomerate and andesite tuff, in which lenticular bands of pillowed andesite are included."

Jan 1, 1954